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HobbySpacer writes: "XCOR
announced the success of the first phase of flight tests
for the EZ-Rocket. In the most recent flight, Dick Rutan fired both of its rocket engines to take off and reach a speed of 160knots and an altitude of 6200 feet. The vehicle is a Long-EZ kit plane modified to hold
twin 400 lb thrust rocket engines fueled by isopropyl
alcohol and liquid oxygen. The project is not aimed at a homebuilt EZ-Rocket but will demonstrate safe and reliable rocket propulsion.
The primary goal is development of reusable launch technology that leads next to a high altitude sub-orbital rocket vehicle for
space tourism,
rocket
racing (e.g. vertical drag racing at air shows) and the
X-Prize competition."

Rockets are the most inefficient method of propulsion that's still in use, a better goal would be figuring out an entirely new propulsion system that could apply to everything. Speaking of which, what's the latest on Ginger?

And furthermore, who cares about "vertical drag racing"? Drag racing cars is fun because it's something everyone can relate to. Very, very few people can relate to racing rockets.

I do not know what kind of efficiency you mean, but in terms of energy efficiency rockets are actually very good. A rocket engine transforms about 90% of the chemical energy of the propellants to kinetic energy. This is excellent.

The total energy efficiency of an orbital rocket can be defined as the potential energy of the empty rocket in orbit divided by the chemical energy in the propellants. Even here rockets are not that bad.

If you have a hydrogen powered rocket with a specific impulse of 4300m/s and a total delta-v of 9000m/s, your mass ratio is 8.109, so the propellant weighs 7.109 times as much as the empty rocket. But the empty rocket has a specific kinetic energy of about 30 MJ/kg, whereas the propellants only have a specific chemical energy of 11MJ/kg. The total efficiency is thus 30/(7.109*11)=0.38. Not too bad, eh?

The reason rockets are still so expensive is that most current rockets are direct descendants of ballistic missiles where cost was not important. And the shuttle is a f***ing joke.

Rockets are the most inefficient method of propulsion that's still in use, a better goal would be figuring out an entirely new propulsion system that could apply to everything

Got any ideas? Once you're at the edge of the atmosphere, you're pretty much limited to using a self contained reaction motor.

Ground laser launching relies on superheating air, plus it's only been used to shove vehicles directly up, so it's basically a really cool but expensive way to replace July 4 bottle rockets. A more viable alternative is turning beamed EM into electricity then powering magnetohydrodynamic motors that superheat air, but you still have that pesky problem that you are relying on an atmosphere to get your speed.

You could accelerate the vehicle in a rail gun or rocket sled until it reaches orbital velocity while it's still on the ground. Ballpark figure, at a (barely) survivable 20g, you'd need a 150km track to reach the 7.73km/s orbital velocity of a typical shuttle mission, ignoring air resistance. Except you can't ignore air resistance, because at 7.73km/sec at 1 atmosphere, you'd burn the vehicle to a toasty crisp.

Even if you postulated antigrav, you still need to generate lateral acceleration to achieve orbital velocity, which again requires a self contained rocket, or an atmosphere.

A beanstalk (space elevator)? Heck, maybe we've already got the technology to do it, but we're not going to, not for a long, long time.

So, really, if you've got any ideas about what to use as an alternative to rocketry today, let's hear them. I'm fresh out.

Well...if beamed EM to electricity is viable, then how about using that to heat self-contained propellant? Sure, it's technically still a rocket, but most of the reaction energy comes from outside the ship, so it's not 100% self-contained.

Or, once you get going at a high enough Mach, atmospheric friction will turn air into plasma. Use standard magnetic controls to keep this plasma off of your craft, trapping the plasma so it itself is what impacts even more air and turns it into plasma, then send this plasma out the back. Basically a more ambitious version of the SR-71's "aerodynamics only seal up when heated by fast travel".

And, of course, there's direct interaction with the Earth's magnetic field - though that takes a lot of power, especially at those (relative to significant magnetic field strength) low altitudes where the atmosphere exists.

Ground laser launching relies on superheating air, plus it's only been used to shove vehicles directly up, so it's basically a really cool but expensive way to replace July 4 bottle rockets.

That doesn't make sense. Isn't going up the hard part? Consider the S1-C Stage [nasm.edu] used in the Apollo missions. It expended 5 millionpounds of fuel just to lift the rest of the hardware out of the mesosphere. This compares to 1 million pounds get the rest of the way, and a few thousand pounds to get back. Finding a more efficient alternative to such a large, expensive, non-reusable vehicle wouldn't complete eliminate the need for rockets, but it would certainly make a big difference in the cost of space exploration!

Uhhh... no. Going sideways at 7.73 km/s is the hard part. Once you hit that speed (assuming you don't burn up, which you would, so you have to accelerate as you rise out of the atmosphere), you'll rise to 300km and stay there. If you just rise to 300km with no angular speed, you'll come straight back down again. Not much use for putting satellites into, what's the word... orbit.

OK, I'm no engineer, and I never really looked at this idea before I read your jibe. But if I understand this explanation [osd.mil] of laser propulsion, there's no reason the thrust has to be strictly vertical. The thrust comes out of a nozzle, just as with a chemical rocket.

if I understand this explanation [osd.mil] of laser propulsion, there's no reason the thrust has to be strictly vertical. The thrust comes out of a nozzle

...in theory. The last that I heard, Lightcraft are still at the stage of shooting tiny disks straight up in the air, with no nozzles or lateral motion.

Actually, that's not strictly true, the disks do experience lateral forces - when the reflective base fails catastrophically in one area and explodes, or when the disks pick up a wobble and tumble out of the air.

It's a truly appealing idea, but (again, AFAIK) the practice is lagging way, way behind the theory. I'm having a hard time picturing them getting anything into orbit without dropping it or frying it to a crisp.

Perhaps our best hope is that Son of Star Wars spins off some useful technology in this area.

So laser propulsion has a dubious background and a poor track record. So did rocketry at one time. You could argue that rocketry still has a poor track record. In any case, I think it's silly to pre-judge all the alternatives to rocketry as pure pipe dreams.

Excuse me if this comes across as a flame, but you only seem to want to look at arguments that LP is a boondogle. Did you even look at the link I provided before? Or have you seen these proposals [llnl.gov]?

None of which means I care for all the "Star Wars" nonsense that seems to be associated with alternative propulsion technologies. Weapons of mass destruction can't be handled by some fancy technofix. But perhaps thats what really has hurt oddball systems like laser propulsion: they have an unfortunate association with folks motivated by nationalistic ideology or military career-building -- not a geninuine interest in space exploration.

But this association shouldn't prejudice us against the very idea of finding alternatives to rockets. As the guy who started this thread pointed out, it's a damned inefficient means of propulsion. A serious return to space just isn't going to happen until we find an alternative.

you only seem to want to look at arguments that LP is a boondogle. Did you even look at the link I provided before

Er, yes, and I've looked at all the pretty concept art that looks like it's been done by the same guy that drew all those flying cars back in the 1950's.

Again, I really like the idea of light propulsion, but the reality is a long, long way off. That's not to say that we shouldn't pursue it, only that we should be careful about throwing money at it just because it's appealing and exciting. The results (so far) simply don't justify it. Once it works reliably for simple toys, then I'd be 100% behind scaling it up, but the proof of concept has to come first.

The "rocket sled" (actually a linear induction motor used as a railgun of sorts, also called a mass driver by Gerry O'Neill and company, and first dubbed a "catapult" by Heinlein and something totally else by Clarke) doesn't have to accelerate the ship to orbital speed. That's ludicrous.

It merely has to replace the first stage, and that only requires a few miles of track, an upwardly sloping mountainside, and a few G's of acceleration. One the ship leaves the mouth of the catapult, it's moving fast enough for a very small fuel tank to kick it all the way to orbit -- not to mention the fact that at mountain height, it's past a goodly chuck of the atmosphere pretty quickly.

It's surprising how little ship you need to achieve orbit once you get rid of the first few miles and get some speed buildup. The ship is SMALL.

A catpult would prolly use maglev, be pretty cheap once the thing is built, and only require electricity to operate instead of rocket fuel. And it is reusable to a ridiculous degree.

Well, you couldn't get orbital speed in the atmosphere, so the track doesn't have to be that long.

We build interstate highway systems that need rebuilding every few years, and no one notices the cost. The track would cost tens of millions, maybe hundreds of millions. The first one would, any way, because it's all new engineering and that means mistakes and redos. The successor catapults would be cheaper.

Back to the answer: you only need to get the ship going a bit -- and I don't have the maths, just the studies over the years by NASA, the National Space Society, endless seminars, fifty years and more of maths, starting with Sir Arthur Clarke -- you need to get the ship up the first few miles, and moving at a few hundred miles per hour, to totally eliminate the need for a first stage. Remember, the first stage is the biggest, and the reasons for that are that it's in the densest part of the atmosphere, and is lifting not only the entire structure of the successor stages and the the orbital craft, but it's OWN weight and the weight of its fuel, an enormous sum.

And don't forget, you can't get it going too fast, or sonic booms play havoc with the catapult, and friction fries the ship itself. No, you can't get orbial velocity in the atmosphere... but you can get the puppy moving pretty fast before the rockets kick in.

Kick out the first stage, and you can have your spaceplane without a giant fuel tank and strap-on boosters. Something the size of a big Lear jet, maybe.

Also, if you want to launch unmanned vehicles, you could harden the payload to take many more G's, and boost that acceleration UP, getting a huge piece of orbital velocity out of the way.

Piece of trivia: remember "When Worlds Collide", the George Pal SF movie of the fifties? They used, yup, a railway up a mountain to get the ark up to speed before the rockets cut in. I remember watching that image as a kid...

The maths and studies have been done over and over again, and they are buletproof.

I'm kind of assuming that it takes power to stay up. Plus, you generally want satellites to orbit. Geostationary? Although if you can shove things out to the moon and catch them there, you can fuel and launch them on much more cheaply.

Hey, when you come up with a propulsion system that has T/W > 1, let me know. Until we can get off the ground with something else, the really cool and exotic [and, yes, efficient] stuff--like ion propulsion, ram jets, et cetera--is going to be the domain of spaceflight only.
Even then, you're going to have to get that stuff up there somehow.
Too bad people are so scared of using fission to provide heat energy for conversion into propulsion [and onboard power]. That could make things really easy, actually...

No, actually a ramjet is way more efficient than a rocket.
A really good rocket motor gets an Isp of just over 400. (A little more if you feel like using F2 or ClF5 or other really nasty stuff, but nothing that dramatic.)
A ramjet gets around 3000. It's a lot simpler than the rocket, and it doesn't have to carry it's own oxisizer, so it stands to reason.
On the other hand, it doesn't work in space, and it needs to move a a pretty good speed before it starts working at all./August.

Think of how much money goes into car racing. Rocket racing would be an incredible spectacle.

Yes, but think about the audience for auto racing - namely rednecks. Rednecks like auto racing because they drive too and watching people drive cars fast apparently makes them think their dick will become larger when they drive their trucks fast. I say apparently because I don't know since I think auto racing is boring and stupid.

Rocket racing won't have an audience because rednecks *don't drive rockets*. Despite the obvious phallic look of rockets, rednecks will not go to rocket races in droves.

Furthermore, auto races are confined to small stadiums where the cars tediously go around and around the same tiny track many times. Rockets cannot be confined to such a small sanitized "track" and instead will blast-off in a few seconds never to be seen again. I suppose rocket racing is more akin to the even more boring drag racing [draglist.com] which has a much smaller audience.

Geeks, the only remaining potential audience for this will go to something significant like STS [nasa.gov] launches. STS = the space shuttle program for those not in the know.

That leaves redneck geeks as the only people who will go to rocket races!

Rocket racing would be an incredible spectacle... but it'll be hard to get much detail. You'll have to watch from far away for safety and perspective reasons--if you have ever been to any CART or NASCAR race, you know you just feel the cars go by you, really.

As for profit potentials, I'll agree that they exist, but at this point, no one's put up the money to make it happen. That we've seen scads of money thrown after bad business ideas in the last 25 years tells me something about the risk/reward function on private orbital flights.

Is it just me or does anyone else think that pushing the limits of rocket design technology at public airshows might not be in the best interests of public safty?

In conventional top fuel drag racing when things go wrong which they often do it can often result in part flying off 100's of meters into the air. Dragsters by their very nature are stressed to the limits of their durability, in order to get that little bit faster than the next guy.

I don't think we want distasters reminisant of the challenger disaster happening at airshows before we decide this is a bad idea.

Areal and nautical speeds are measured in knots, not miles per hour, or km/h or cms.
Force of engines is measured in kilonewtons, not newtons.

But what would you convert the units into? Metric, or regular.

The whole idea of metric is that we should put all of our eggs in the one basket, so that people with certian brain defects would not be able to understand it. I found little logical in it to understand what people see so wonderful in it, and I have studied it for thirty years now.

Imperial, freezing is at 32, boiling at 212
celcius, freezing at 0, boiling at 100

Nothing special about these temperature points. The only one that matters is absolute zero = 0. I mean, there are 180 degrees fahrenheit because of historical accident, but at least Fahrenheit adjusted his scale so that fractions would not occur in normal use. The original Roemer units were four times the size. (ie Fahr / 4 both size and scale).

Reameur scale is at least logical in that its degrees represent the increase in volume as 1000 units of alcohol are heated. It ranges from 0 to 80.

Without further comment, the Celcius temperature had freezing at 100, and boiling at 0. The current scale was called Centigrade, but Celcuis was coopted when everyone forgot about the mark I fiasco.

AngleYes, the wonderful simplicity of the metric system, which was intended to replace all measures, did supprisingly poor on angle and time. Despite the so-called decimal advantage, and that the kilometre was intended to be a centisimal minute at the surface of the earth, and so replace nautical mile, neither the decimal division of the quadrant, or day took off. When you calculate the speeds in decimal days, you will start to see the silliness of unrestrained decimals:

Distance. A furlong is 660 feet, as anyone can see. A mile is clearly 5280 feet, as it should.

Imperial ounces don't exist. They're avoirdepoise, troy, or fluid ounces. The context defines the missing adjective. Just as it does with cubic, square and linear measure.

And while you're at it, I notice that you are supprisingly silent on mill, a length, angle and volume, or K, a number, temperature, distance, mass, speed. The truth is, that relying too heavily on a matrix naming does lead to lots of confusion. We won't even go into the prefixes like deci vs deka.

10 mm to the cm
100 cm to the meter
1000 meters to the kilometer

1000 ml to the liter

It is of course interesting here, that apart from preaching how the metric system uses prefixes and so forth, how the "centilitre" is noticably absent. Even more so the nightmare of deci- vs deka, hecto, or Myria-. Oh well. There goes consistancy.

Both systems suffer from the Roman weight-fraction legacy. An uncia was a 12th measure, this gives the foot of 12 inches, and the troy lb of 12 ounces, and an hour of 12 ounces. Mind you, any metric unit divides into 1000 mills. Depending on context, the builder's mill is the mm, where the chemist's mil is a ml. And we won't even worry about "gammas", a mass and magnetic field, and "lambdas" a volume, and "micros" a mass, not to be confused with "microns", a length, or "ohm", a capacity and resistance unit, or "farad" (a capacatance) vs "faraday" (any of a number of electrical charge units).

Metric is still bound by the same sorts of mentality that drives the imperial system. One talks of millions of kilometres, not *gigametres, or "tonnes", not "Megagrams". So much for "logic". Mind you, the names are wildly long that people look for shorter names.

And we won't even worry too much about a large number of special symbols that you need to express its units (eg raised 2, 3, greek Omega, mu). Like, you can't write sq m, you have to put m^2. Where I can write ft or Ft or FT, mm, Mm and MM can be milli or mega- metres.

What's even more impressing is that the prefixes are both patchy, and overload letters, for example, m and M differ by nine orders of magnitude (milli, and mega), and somewhere we got to squease a third m for micro into this lot. Luckily, we can steal the greek mu for this end.

The whole prefix multiple system has been coopted into computing, where one can use K as 1000 or 1024, depending on what your needs are. Megs, Gigs and so on are simply K*K, K*K*K &c. So a 1.44 MB floppy is actually 1.44 * 1000 * 1024. Hmmm.

Metric is MUCH simpler than imperial.

I seriously doubt this, too. The numbers that metric are easier to convert between one and another unit, but I can not seem to recall doing conversions from capacity to volume units all that often, that rough rules could not handle. But to achieve this simplicity, much had to be sacraficed.

Yes, I am familiar with this definition. I am also familiar with the other definitions. The one that takes precedence is 1 day = 86400 seconds: that is, 1 day = 24 hours, 1 hour = 60 minutes, 1 minute = 60 second (minutes). All other definitions are adjusted to preserve this relation.

Look at the source, not this week's definition. Previously 1 second was a fraction of the mean year 1900.

The whole idea of metric is that we should put all of our eggs in the one basket, so that people with certian brain defects would not be able to understand it. I found little logical in it to understand what people see so wonderful in it, and I have studied it for thirty years now.

Umm, no. The beauty of metric, or rather the more modern form of metric called SI (Systeme Internationale) is that:

a) multiples of a unit are always in base 10, so it is obvious that 27km = 27000m, and it is just as simple to write that in scientific notation (i.e. 27km = 2.7x10^4m) - you try telling me what 27 miles is in feet without reaching for a calculator

and b) there is a small set of measured base units (there are 7 - metres, kilograms, seconds, amperes, kelvins, moles and candelas) and every other unit used throughout science and engineering is directly derived from these base units without any fudging

Quite apart from the obvious benefits for calculation, it also makes things much easier to understand in your head - you only need to know the size of the 7 base units to be able to have some idea of exactly what each derived unit means. Also, if you are sticking to SI notation to the letter, it is plain from the name of the derived unit exactly how it is derived from the base units.

Really, it is perfectly logical, and a heck of a lot simpler to learn than the old Imperial or Imperial-derived systems, where there were about 3 times as many different base units. Science has adopted SI worldwide, partly for its ease and simplicity, and yes, partly because scientists want to be able to understand each other. In most countries, engineers have also adopted the system for similar reasons, and even the general populace understands most of it thanks to everyday things being measured in SI units or multiples of - masses in grams or kilograms, volume in litres, distances in metres or kilometres.

Volume: one litre is the volume of 1000 cubic centimeters (i.e. 10cmx10cmx10cm cube). How many of you can tell me how "large" one gallon is, physically? Could you guess how many gallons are in your swimming pool just by the dimensions... in your head?

Kilogram: the mass of one litre of pure water. How much does a gallon of water weigh???

Metric Tonne: the mass of one cubic meter of water. How many Imperial Tons does your swimming pool weigh?

I can easily visualize things in terms of metric units... but it's very difficult to do so with Imperial units. I see this as a great aid in any sort of mental gymnastics.

Isn't this a dead give-away. System = collection of units used together: International = hodgepodge designed to clip the wings of foreign aspirations. Enough said

..it also makes things much easier to understand in your head..

Actually, you would more easily understand the intensity of a kilometre-candle, (ie a candle at a kilometre), rather than a metre-microcandle, (ie a millionth of a candle at a metre), which is what a microlux is all about. Also, an acrefoot is an easier volume to grasp than a Megalitre, although they're the same size. People convert sheets of paper into stacks miles high because thousands and millions can not be grasped.

7 base units

CGS had only three, and seemed to work OK with that. I've used systems with one base unit. All this means is how many equations you plan to leave out of the derived theory.

They only have seven, because the the system is a botch-up that they HAD to have 7. The mole was only invented as a base because SI did not want to use the coherent kilomole. The base unit "Ampere" depends on the size of the metre and kilogram, but the "Henry per metre" is free of such dependancies. Yet the "Ampere is afforded the status of "base unit". The size of the candela depends on the square metre, but the lux does not.

Sad about the mass unit having a derived name...

you try telling me what 27 miles is in feet

Don't have to. Because I don't do that sort of conversion at all. Really.

be able to have some idea of exactly what each derived unit means

Some is the operative word here. Rationalisation throws a spanner in the works. 1 C translates into 12.566 C, if flux is being refered to.

Really, it is perfectly logical, and a heck of a lot simpler to learn than the old Imperial or Imperial-derived systems, where there were about 3 times as many different base units.

The imperial system has three base units; yard, pound and gallon. All the rest are supplemental. Somehow, three by seven is three. Good one.

Also, if you are sticking to SI notation to the letter, it is plain from the name of the derived unit exactly how it is derived from the base units.

I did way better with no units, in a google system. In essence, 1 s = 1e100, 1 m = 1e1100, 1 kg = 1e73300, 1 A = 1e32100. Decimal prefixes are just added in: 1 cm = 1e1098. Do unit and exponent calculations all in the same column. The units are far enough apart that you can do the unit sums and exponents with a calculator, and you don't have to remember individual dimensions.

yes, partly because scientists want to be able to understand each other

The pre-metric system used by scientists was Paris feet. Not having a precise widely used measurement system does not hinder much of science.

Why measure volumes in litres. Doesn't the cubic metre cope with this??? No. Volumes are derived from the linear measures, and are very hard to reproduce. Capacity is done by bulk comparison, and is very easy to use: ergo, litres, gallons, bushels.

Also, if you are sticking to SI notation to the letter, it is plain from the name of the derived unit exactly how it is derived from the base units

And from this, we can see immediately how "Weber" is derived from "Metre", "kilogram", "second", and "ampere". Get real.

The number of base units is not a fixed constant, but an arbitary statement of unit derivation. In the imperial system, time, temperature, moles, light and angle are all supplemental scales, not units to be defined externally.

So where the CGS mole is derived from the gram and the the fps, the lb-mole derives from the pound, the SI mole does not coherently derive from the kg, so they had to invent a new base unit for it, and deal with it separately.

Leo Young had six base units where the cgs has three and the SI has four.

The metre is currenlty defined as 1/299792458 light seconds. From 1900 to 1963, the litre was defined as the volume of a kilogram of air-free water, at STP, and was 1000.027 cu cm water. The Litre is not "a handy unit": reproducing volumes by bulk comparison (ie pouring or weighing) is more accurate than from its linear measures. Dry capacities (grain, fruit and so on), dropped out once scales became cheap enough to enter the market place, around the 1870's or so.

I have a whole range of physics where the volume of a cube is six times the cube of the side. You just don't know that there is more than one "multiply" hanging around [hint: think of dot vs cross products]. The definition of the square and cubic metre are in fact, semi-base units. This is because the multiplication is not unique.

Isn't this a dead give-away. System = collection of units used together: International = hodgepodge designed to clip the wings of foreign aspirations. Enough said WTF are you talking about? Care to explain this? Obviously not enough said.

Actually, you would more easily understand the intensity of a kilometre-candle, (ie a candle at a kilometre), rather than a metre-microcandle, (ie a millionth of a candle at a metre), which is what a microlux is all about.
Of course, had you any idea what you were talking about, you'd know that microlux is not an SI unit. The candela (cd) is the unit of luminous intensity.

The intensity of light in this item was originally measured in foot-candles, the intensity at one foot from one candle. Now, the metre-candle is called a lux, and a microlux is either a kilometre-candle, or metre-microcandle, both of which is 0.000001 lux, or one microlux.

An acrefoot? lol. Ya, that's real intuitive for people who have heard of neither acres, nor feet.

Nor are litres and metres, for people who never seen them. Most people have difficulty grappling with visualising large numbers, anyway.
When I tried to visualise the scale of the WTC, I chose to multiply a skyscraper by five, rather than the house I live in by 55.

Also, once again if you knew what you were talking about, you'd have known that the liter isn't an SI unit either. Volume is measured in cubic meters which is very easy to grasp.
It's actually in one of the supplementry tables.

Perhaps for simple minds. You telling me you can't grasp 1 million dollars?

A million here is a quantity, not a number.

They only have seven, because the the system is a botch-up that they HAD to have 7.
No, you see it's called good design. You put something in if it makes sense that it should be there, because it is, in fact, a distinct entity.
The mole was only invented as a base because SI did not want to use the coherent kilomole.
The mole has been around since 1850. It was accepted as a base unit in 1973 or something. Reason, because chemists regard the mole as a derived unit. SI upsets the mass-mole relation, so they had to make it a base unit.

The base unit "Ampere" depends on the size of the metre and kilogram, but the "Henry per metre" is free of such dependancies.

Read the definition of the ampere, and do the maths of actual dependancies, before you objec to this.

The henry is m^2kg/(s^2A^2), therefore the "Henry kilogram per meter squared" is free of them.

Whence A^2 = kg.m/s^2.[H/m]

The lux is derived and is defined as: cd/m^2.

Two paragraphs ago, you said the lux was not an SI unit. Actually, the lumen is the base definition.

Some is the operative word here. Rationalisation throws a spanner in the works. 1 C translates into 12.566 C, if flux is being refered to.

The flux of an souece can be measured in different ways. In CGS electrics, with light, and so forth, unit flux intensity is had at unit distance from unit source. The total flux over a sphere is then 4pi of that source. Rationalisation makes the total flux the same as the source, and so factors of 4pi creep in.

The pre-metric system used by scientists was Paris feet. Not having a precise widely used measurement system does not hinder much of science.
This is known from reading material. It is the unit that Newton and Coulomb worked in, for example.

Yes actually. Volume is not measured in liters, but in cubic meters. Capacities are'nt though.

Considering that you've made a fool of yourself in this post by trying to criticize something of which you apparently know very little, you now have zero credibility.

Oh well, none of your comments stuck. Maybe you should take the foot out of your mouth, and use it to head off to the library and do some research, first.

You seem to be confused again: intensity is not the same as intensity over an area. Candela is intensity, lux is intensity per unit area.

A good units dictionary should tell you that the lux is the new name for the metre-candle. It follows any unit Length-Source is the intensity of flux from a source at distance Lenght from it. From the example I used, it was intended to be an intensity some distance from a source.

I'm sorry, perhaps I have to repeat myself: the liter is not an SI unit. Understand?

Any unit intended to be used as part of a system is part of the system. Anything over that is unbridled pedentry.

Acrefeet use two combined units of measurement to convey the same amount of information; that seems quite useless and unnecessary.
So is Coulomb-metres, Ampere-hours, metres per second. It's called "multiplication".

A million here is a quantity, not a number.
What's the difference?
Quanties are measured, and change when the units do. Numbers are counted, and do not change. So a "million dollars" is entirely different animal to "one million one-dollar coins". Most people who have a million dollars do not have it all in one-dollar peices.

The mole has been around since 1850. It was accepted as a base unit in 1973 or something.

The mole appears as a derived unit in the International Critical Table of 1922, as a long established unit. It did not become a base unit until 1973. Reference for this is a number of unit dictionaries.

All my claims in my previous post were referenced and backed by a government-run science-oriented website.

The sort of site that you refer to reflect current prefered usage, not historical development. You obviously chose to ignore the definition of "ampere" there.

I know very well the def'n of the Ampere; I'm an electrical engineer, I use it every day. The Ampere is a Coulomb of charge passing a point per second.

It's actually defined in terms of Ampere's law, applied to two infinite conductors placed one metre apart. One ampere flowing through each of these conductors will exert a force of 2e-7 Newtons per metre of conductor. The definition has three variables, R=distance apart, L= section of conductor, and F=force. The maths cancels out R and L, so you can replace "metre" with "foot", "centimetre" or "mile" without upsetting the definition, but the ampere depends on sqrt(Newton). When you subst "(kg.m/s^2)^1/2" for "A" in the definitions, you will see that the "H/m" becomes "1", ie is independant of the size of the metre, kilogram and second.

Once again, you seem to be seriously misunderstanding the meaning of base and derived and convey to me that you have a very shaky understanding of mathematics:
1. y = x + 1 (look! y is a function of x!)
2. x = y - 1 (gasp! now x is a function of y!)

This is because I bothered to check the "definitions", and worked out what is truely independent. The choice of H/m was not accidental: it's the unit of the magnetic permeability, which is, when you read the definition of the ampere, the thing actually being defined.

Two paragraphs ago, you said the lux was not an SI unit. Actually, the lumen is the base definition.
lol. You're too funny. The lux is not an SI unit, and nowhere did I say it was. I said it was a derived unit and has the following relationship: cd/m^2.

We both made errors here. Let's call this one quits, and note that the lux is an SI derived unit = cd sr/m^2. The latest definition of the candela goes through the lumen, and depends on the size of the Watt.

Well obviously you're dealing with a completely different situation then. You're dealing with flux over a unit area in the latter case versus flux over unit distance in the former, so C does not magically equal 12.566C. I don't see what the problem is here. What is your point?

He's an electrical engineer, and has never heard of "rationalisation", where the factor 4pi magically shifted around equations. In the cgs system, total flux from a point charge is flux = 4pi charge. In SI, it is flux = charge. So a coulomb of charge gives 4 pi C under a non-rationalised system, and 1 C flux under a rationalised system. Hence 4 pi C (unrationalised) = 1 C rationalised. Same units, same dimension, different numbers.

This is known from reading material. It is the unit that Newton and Coulomb worked in, for example.
You wanna bet how much of a pain it is? Remember the Mars craft which was fed incorrect values due to unit conversion?

You should read the footnote where Maxwell comes to the conclusion that light is an vibration in the electromagnetic ether. It's got a hideous number of units, and some mis-conversions in that as well. He confuses the sea mile (6000 ft) and the nautical mile (6080 ft).

Capacities are'nt though. Why not?

They should be since capacity and volume are the same type of measurement. Except that bulk comparisons are more accurate in commercial applications then linear measures. Hence the different names.

Sorry, but bragging doesn't work for people who are wrong. You should really try thinking and doing some of that research yourself. Perhaps you can start by reading that website I linked to. I'll make it easy for you: it's here [nist.gov].

Sorry, I am not wrong. A technical education does not make you a historian in weights and measures. It means that you know how to put wires into things. Understanding the history and basis of weights and measures is a different field.

Any unit intended to be used as part of a system is part of the system.

It's nice that you argue that the Imperial system is a coherent single system, despite the different capacitity systems between the US and UK, and when the Russians used the foot, they did not use the pound. On the other hand, the metric system called SI, which is used with Litres, is somehow a hodgepodge of different systems.

Quanties are measured, and change when the units do. Numbers are counted, and do not change.

Things that are measured take singular: money is coming in from..., where counted things take plural: cattle are coming in from...

I never argued any history with you, but argued statements you made about SI. Therefore discussing SI as it currently stands is the issue on the table.

But that did not stop you from demanding the source for the recent status of the mole. Historical prospective makes metrology easier to understand.

Notes on the definition of "ampere".

Unlike the other definitions, the ampere is defined to set the permeability of free space to a fixed value. Specifically, it can be written so that it is 1e-7 H/m.

The practical electrical units were defined to be a decade multiples of the theoretical EMU, for "practical applications". Any system that has an energy unit of a Joule, and a time unit of a second, can absorb them. In SI terms, this means a length of k metres, and a mass of 1/k^2 kg, the resultant permeability constant is (1e7)/k Henry/Length.

Maxwell puts k=1e7, which makes L=Quadrant [of the earth, = 10,000 km (hence the old name of the Henry), and M = 1e-14 kg.

. The system derived is coherent with the EMU equations.

In order to have k != 1e-7, you have to rewrite the EMU and divide quanities (eg B from H). You could define k or L. Gustav Mie defined L=1 cm, and hence k=0.01, M=10 tonnes. Giorgi puts L=1 metre, so k=1. This is the basis of the MKSA, and hence the SI.

If you chance to visit your NIST site, download sp330.pdf, and look at the adobe page 67 of that. You will see they talk of a new value for the von Klitzing constant of 25812.807 Ohms. This is 137.036*2pi*29.9792458 Ohms. 29.979&c is the speed of light. The reason that this can not be made the new definition of the Ohm is because it would upset the intended definition of the ampere, as seen on adobe page 68 of that pdf.

Therefore, we are entitled to regard the ampere defined to preserve the permeability of space, and that the H/m as the most important fixed value.

base units, definitions and dimensional analysis.

A definition, can only be true for a specific case. You can not define an equation. There is nothing inherent in the definition of any of the base units, or even in the derived units, that imply the relationships involved.

Units can not be intrinictly coherent. They are coherent to a body of equations. CGS units are coherent, as are SI units. But they are not coherent to the other's equations. And, as a result, the dimensions are not strictly equatable; hence the "equates to" in the conversions.

One has a series of relationships that define things. For example, Force=mass*acceleration, or F=ma. This gives a definition that defines a unit force in terms of unit mass and unit acceleration, under specific conditions. [A definition can not infer a relation, but must infer the things it depends on].

There are units that depend on force, eg power, energy and pressure.

Gravity is easy to use: mass can be converted to force fairly easily. The term "weight" translates variously to a mass "net weight" or statistics, or a force as in mechanics. This leads to mass being used as a force unit or mass force indifferently: eg pounds per sq in.

In the case of the fps system, one can derive an absolute system based on the f=ma relation. Kelvin makes the pound mass, and the f=poundals. Perry makes f=pound, and derives a mass="slug". The practical system is a mix of Perry and Kelvin systems, as gaussian = mixed ESU, EMU.

One can diffirentiate the (mass,force), like Stroud (pound, Pound), or the german style (gram, pond), the US style (M-mass, M-force) or the new style (M, M-force). cf Kennelly's ab-, stat-

One can make all systems coherent by rejecting F=ma as a derived equation, and defining F as a base unit. So you would have ft-lb-pdl-s or f-slug-lbf-s or ft lb-lbf-s, which is how the fourth, electical quantity appeared (as ESU and EMU are cm-g-s-Fr and cm-g-s-Bi).

Alternately, one can divide the force into "force = f=ma" and "g-force=mg". This is how D gets split from E.

Dimensions arrise from a putting the base units as variables, eg L M T F, or L-M-T-g. The number of dimensions is quite arbitary. It's an open algebra. This means, that I can take your dimensions and use it as if I derived it. But if I want to use it in a dead-end calcualtion, I can substitute L, M, T as 0.3048, 0.4536 and 1, to convert fps to MKS, or even put L, M, T as L^1, L^3, T if this needs to be done. It's an algebra, and I can substitute the values.

Young had an algeba that allowed exact conversions between SI and CGS. He had six base units, adding S and U to the LMTI set. U basically corresponds to a turn in "ampere-turn". The HLU and Gaussian has a curl here, ie a Bi = Fr/s - curl. 1 curl= 29979245800 turns. S is the space factor: 1 Coulomb produces 1 C-sur of flux, or 4pi C-sun of flux.

He has a body of equations, and six free variables, or six base units. You can fold the equations to get the SI or CGS equations by substituting for S and U beforehand, or leave the equations unfolded and add two extra base units to SI and CGS.

So how many base units for electricity? four or six?

There is no reason that in future some compelling reason will evolve for us to associate the candela with the watt. I mean, they used to measure resistances in miles (of copper wire).

Capacity

I'm sorry, but I'm failing to see why one would be more accurate than the other.

You are looking at the number, not the practical implication of measurement. Have you ever tried to construct a cube of a specific volume. It's easy to do a cylinder, since these can be turned on a lathe, which is why you see lots of cylinder measures. But a cube?

Technical vs Scientific measurement

The thing that the technical people brought into SI is that every unit should have a name. In science, one can say "in cgs units, and give just the number.

The thing that the scientific people brought into SI is coherence, the idea that one can say: the SI unit of X is Y. In some fields of science, they simply say "in xyz units" and drop the units completely. That's why the CGS units did not have names until Kennelly gave then ab- and stat- names in 1904.

History is important, because it decides the evolving patterns, the candela may be the current "pound-force".

It's nice that you argue that the Imperial system is a coherent single system,

The reason that I say the SI is a hodgepodge is that it is not anything like the sorts of systems that arise from theory. Much of theory had to be rewritten to accomidate the features of SI.

The electrical units pre-existed the MKS by many years: that there was a connexion to be made was only found in 1905. That is, the kilogram is a derived unit in the m-J-s system.

The reason that the mole was elevated to a separate base unit, was that the older dimension was M. In the MKS, this would have made the kilomole the base unit. This is what was actually used. SI gets around using gram-moles and kilograms, by making the mole a base unit.

The terms "practical" and "rationalised", bandied around as if they were things to be valued, actually have quite different meanings.

"Practical" is made out to mean that the units are of practical size. In fact, all it means is that the Joule, Watt, Ohm, Volt, etc, are part of it. The centimetre-dekatonne-second system [Mie] is "Practical". I made one out of the foot-Joule-second as well. V, A, ohm, F, H, second, watt, joule, Wb and C are unchanged. Mass=hile, force = trood, length=foot. J=foot^2*hile/s^2. Make the hile represents the "slug", and 100 degC = 140 degT. A new weight "bess" is needed so that trood = bess-force. In this system, J = foot-bess-force, and kJ=bess * degT * joule constant.

"Rationalised" is made out to mean "rational" or "logical". It actually means an adjustment to bring together values. When the 4pi is introduced into coulombs equation, it makes some measures equal. For example, in polarised media, J, M, P were 4pi of the induced fields B, H, D. After rationalisation, they become equal. Displacement originally referred to the displaced electrical charge P [as in the International Critical Tables], but when P=Di, this allowed D to become also displacement.

In any case, rationalisation means the system was fiddled with afterwards, ie not self evident. Gravity and light have not been fiddled with, so the system is incoherent over this respect.

I never said that imperial wasn't coherent (nor did I say it was).

Sorry: my mistake.:(

On the other hand, the metric system called SI, which is used with Litres, is somehow a hodgepodge of different systems.

If it is acceptable to use it with SI, and other units not with SI, then why reject from the system?

You are the one who originally said SI is a hodgepodge, but now you're saying that it's not? Is this now what you meant? It is essentially what this sentence is saying.

That SI has seven base units where other systems need only three or four, is a pretty good sign.

Things that are measured take singular: money is coming in from..., where counted things take plural: cattle are coming in from...

Very well, so what is this in response to? I don't see how this has much to do with what I said...

It's in relation to the difference between a number and a measure

But that did not stop you from demanding the source for the recent status of the mole.

Of course I did.

Fair enough.

Notes on the definition of "ampere". Are these your own definitions and arguments, or taken from the documents you referenced?
It is a paraphrase of the actual definition, and considerations in the construction of reproducable resistences, as I quoted

A definition, can only be true for a specific case.

You can only define, for example, that a pound-force is the gravity acting on a pound. You can define a function, as well: for example, square ~ as the area of a square of side ~. But you can not then having defined a foot=12 inches, and the relation of square to linear measure, then define a square foot as 144 square inches.
You can not define an equation.

If all the elements of an equation are defined, the equation can not also be defined. The equality is either true or false, or irrelevant.

Define in what sense? I can make up an arbitrary, meaningless equation that has no real world correlation. It's not very useful, but I defined it.

True. That's how most quantities start out: someone defines a measure that is sort of useful.

With the conversion factors placed in the appropriate locations I'm sure they are (I don't see why they wouldn't be), but then again I don't know for certain.

Flux from a charge Q, in SI flux=Q; in CGS; flux = 4.pi.Q

Capacity and Volume

Capacity and volume are the same concept: space, but there the distinction is needed because there are a lot of measures that are not derived from the linear dimensions of the vessel. Is not the imperial gallon derived from the pound?

History is important, because it decides the evolving patterns[...]

Historical ideas are important, because the way we see measures change over time, as does our use of number. For example, around 1900, the style was to use large numbers of small units: CGS, grains and inches. In 1980, the style is to use small numbers of large units, MKS, pounds and feet. You would miss that if you were not aware of it.

Relying on historical wreckage can lead you into the same mistake I heard of about women's feet in China. The servey merely looked at their feet and ages, and noted a movement of the feet in certian trends. This reflects changing customs, not biological presures.

The nautical mile is intended to be a arc minute at the surface of the earth, so that angular minutes are read directly to nautical miles.

An imperial nautical mile is 6080 ft, a metric nautical mile is 1852 metres. The original metric system was intended to be a circle divided into 400 degrees of 100 minutes. In this version, the kilometre would be the replacement for the nautical mile. But the angle system never took off.

So hour is not a metric measure, so why don't you just say 82.3 m/s and be done with it. Or are you going to cling to your illogical hours? For us common folk, 160 knots says it all.

Force of engines are measured in a common unit, which happens to be the kilonewton. Just like clothing is measured in centimetres, not metres or millimetres. Hint: people compare numbers on the expectation that a standard unit will be used where convenient.

can someone tell me why they're not interested in using balloons at all for reusable launch vehicles? It would make far too much sense to me since it's essentially free and lightweight, and a lot LESS expensive than dumping humungous feul tanks into the ocean after every launch. You can get up very high, ditch the balloon, then use attached rockets to fill you the rest of the way. You could even use reusable balloons with hot helium instead in case you need to lift too much weight for just hot air to raise.

If you want to get into orbit, or leave Earth entirely, the crucial thing you have to do is go really fast. Altitude is pretty much irrelevant except that aerodynamic drag slows things down more at lower altitudes.

The only difference than launching from a balloon at altitude would be the slightly reduced aerodynamic resistance, negligible compared to the cost, complexity, and risk of building a floating launch platform:)

Actually, a balloon first stage is incorporated into a number of fairly credible amateur rocket designs. By using a balloon to bypass the heaviest 15-20 miles of the atmosphere, you're cutting down not only on drag, but distance. This means you have to carry considerably less fuel, leading to a smaller, cheaper, and possibly more reliable design. It probably won't be used for getting large multi-ton objects into space, but for a small one-two man capsule, or a small satelite, a balloon launch makes a good deal of sense.

if you can get 16km up (which is pretty easy even with a large load) you've cut out a LARGE portion of the density of the atmosphere. For every 16km up you're down to 1/10th of the density. So 16km up is 0.1atm and 32km up is 0.01atm.

Needless to say 90% reduction in density leads to _significantly_ less air resistance. Now although air resistance is not a huge drag (no pun intended) it does play a part. Add to the equation now that you're 16km up without using any feul, and you have that much more potential energy to use to get up to speed.

And the risk of building that is... negligable. These things are, by definition, aerodynamic. If you drop the plane straight down all you have to do is pull back on the yoke and pretty soon you'll be flying vertical again. The balloon has to do nothing more than just drop the rocket.

The main reason is the FAA. If you want to be a high alt attempt, you need to file a lot of paperwork concerning your flight plan and risks to populated areas/foreign airspace. In theory, you could get approval for an orbital shot from two places in the USA (Black Rock and Alaska,) if you have a self-destruct device on board. Note that a self-destruct doesn't make the rocket vanish, it just puts the debris in a safe zone. Now, if you want to float to 120,000 feet before launch, your debris zone is about the size of the Pacific Ocean. You don't get approval, end of story.

however I don't understand why your wreckage zone is that much higher.

and besides, if you launch from near the ocean and float out into international space, do you still have those problems? surely if you're over the ocean you don't need to worry too much about debris falling on people. Nasa routinely dumps stuff all over the ocean all the time, it can't be that hard to make it a reasonably targeted zone.

The wreckage zone is much bigger for two reasons: you may need to abort during the climb to launch alt, and you don't know where the launch will take place.

Assuming a 4 hour climb, you may pass through the jet stream (giving you a speed of 100 mph or more) and then get pushed around by the stratospheric winds. You might have travelled 300 miles or more in a relatively random direction. From this unknown location, you fire your rocket. In this thin air, it easily reaches Mach 4 and starts to go off course. You abort, and put the debris into a nice lob in the thin air. This gives you an additional couple of hundred miles in a random direction.

Ok, I exaggerated a bit - the debris zone is in the 100,000 square mile range: the FAA wants numbers that show the chance of hitting a ship is.1% or so, airplane 1 in ten million or so. Plowing in foreign soil is a no-no. In theory, you could get the waiver, but it still seems easier to just tank up a big dumb booster, ideally launched from White Sands or similar, so you can avoid the FAA red tape.

They were invented by Dr. Van Allen and some of his associates. They were only for sounding rockets, which explore the upper atmosphere but don't go into orbit. If you want to go into orbit, you still need a lot of horizontal velocity so the rockoon is not as handy for that.

JP Aerospace [jpaerospace.com] "America's OTHER Space Program" is doing this very thing. They used balloons to carry a launch platform and rocket to 26,000 ft where they launched the rocket. Now they're currently working up to being able to launch from 100,000 ft.

"The primary issue with getting into orbit isn't going up, its with going sideways at around 17,000 mph."

True. On the other hand, there are definite advantages to getting above a high percentage of that pesky thick layer of air that seems to blanket this planet.

* There's a lot of aerodynamic drag associated with the passage through the dense atmosphere at low altitudes Ever notice the Shuttle and other rockets throttle down at the "max Q" (maximum aerodynamic pressure) point? That (inefficient) action is necessary to limit the forces so the vehicle won't break up.

* Although the altitude balloons can reach is much, much less than that of orbit, there is still a measurable advantage in necessary delta-v (velocity increment needed to reach orbit) from a high-altitude launch. I haven't look at the exact numbers in years, but it's on the order of percents--not insignificant when dealing with the tight margins inherent in launching.

at 100,000ft you are not only at 10% of the original density, but you also have a lot of mgh potential energy. So you drop at an angle and you can get your vertical velocity up VERY FAST with a lot less propellant. Drop for about 10 seconds and then kick in your rockets and you're far ahead of the point where you would be if you had used only propellant to get there.

And if you're wondering about orbital/escape speed, it's roughly 7KM/s for orbit and 11KM/s (which is root2 * 7KM/s) for escape, but these are fallicies. You can technically escape the planet at a velocity of 1cm/year, and you can also orbit at 200M/s. However using the GMM/r^2 = mv^2/r (which is how you determine all this from the beginning) at a distance of 0m off the surface you're at 7KM/s orbital speed that decreases the further that you get away from the planet.

Go check out the JTrack 3D satellite tracker to get cool information about all of the orbits/speeds/etc of all of the satellites orbiting our planet.

Now, not only do I have crapily modified cars running down main street fridays and saturdays, but now I also have to deal with these jerks interruptin my flight!? I don't want to see a rocket with a 4' muffler, it's not cool. I don't care if your rocket has a Vtec engine. I want to fly safely from point A to point B, much as I would like to drive from point A to point B without having your terrestial counterpats fly past me at 100+ mph.

The first tourist in space got to stay on the ISS for a couple days and he was using a well tested reliable vehicle (Soyuz). The tourists of these sub-orbital rockets would get minutes (at most hours) in a cramped vehicle, is it worth the risk ?
Although I agree with the concept of stimulating creativity for designing sub-orbital re-usable vehicles, keep in mind that these "tourists" would still be essentially strapped to a liquid oxygen bomb and that if "civils" start going into space what does that say about the gruelling Astronaut selection performed by NASA and all the space agencies that produce astronauts (Russia, ESA, CSA, NASDA,ISA etc.)
These people (astronauts) give up a good part of their life to get a trip into space. Challenger was the first to fly a "tourist" on the crew and we know what happened. NASA then cancelled all civil/commercial endeavors using the shuttle ever since...
In my opinion the risks are too great to let just anyone fly in these vehicles. (as payloads mind you)
-I am tempted to use the cliche "Talk about the Wrong Stuff"

it seems like the server's going down (or it could just be australia's crap old ADSL) So here's the body text, fear my karma-whoring or something.

Mojave, October 3, 2001: XCOR Aerospace today announced that it has successfully completed the first phase of its flight test program for the EZ-Rocket. The EZ-Rocket is the world's first privately built rocket powered airplane.

At 0900 hours today the EZ-Rocket took off from the Mojave Civilian Flight Test Center to an altitude of 6,200 feet before gliding back to Runway 30. The EZ-Rocket is powered by twin 400 pound thrust rocket engines designed and built by XCOR Aerospace. The flight test program passed its first milestone by flying with both engines for an engine run time of 96 seconds and total flight time of five minutes and twenty seconds.

Retired United States Air Force Lieutenant
Colonel Dick Rutan

XCOR's test pilot is retired United States Air Force Lieutenant Colonel Dick Rutan, a Vietnam veteran and world-famous test pilot. "I ignited one engine and the crew said everything looked good, so I lit the second engine and we started moving," said Lt. Col. Rutan. "As I rolled down the runway Mike Melvill flew overhead in another Long-EZ and served as chase plane. The plane took off 1,200 feet down the runway and once airborne the vehicle rapidly accelerated to 160 knots. The rocket power provided positive, firm acceleration. Once we started running out of liquid oxygen I shut down both engines. Mike inspected the airplane visually and reported it was clean with no leaks. We entered a standard flame-out [landing] pattern and glided back to the runway."

The EZ-Rocket is a research and development test bed for XCOR. "Routine operations must be the primary criterion for rocket engine development," said XCOR Chief Engineer Dan DeLong. "Our approach is to build safe and reliable rocket engines first, then progress to the higher performance needed for orbital launch vehicles."

XCOR president Jeff Greason said, "We passed a major milestone today. This is a significant technical achievement for a variety of reasons. First, once you get two engines working in combination it is significantly easier to cluster more engines for larger vehicles. Second, we were able to keep the engine and fuel flow running smoothly during the flight."

The official roll-out and flight demonstration of the EZ-Rocket will take place this November at Mojave airport. Check the XCOR (www.xcor.com) web site in the next few days for details on the event.

EZ-Rocket SpecificationsThe EZ-Rocket is a modified Long-EZ homebuilt aircraft. The aircraft is powered by twin 400 lb thrust regeneratively cooled rocket engines and fueled by isopropyl alcohol and liquid oxygen. The EZ-Rocket includes an external composite fuel tank and an insulated internal aluminum liquid oxygen tank. The modifications were performed at XCOR Aerospace's Mojave, CA shop. Tests are performed at the Mojave Civilian Flight Test Center.

It looks like Buzz Aldrin's got some competition now.... Buzz had been going at it with the idea of adapting existing missile tech in clusters to form a cheap booster for commercial space.... but it looks to me like he was using the cathedral method of design. Big and slow.

On the other hand, it looks like the Rutan brothers are using something like Extreme Programming to build rockets... build up little by little, test daily, twice, three times a day, use existing airframes as testbeds (Dick Rutan could fly a LongEZ in his sleep, and probably has by now:).... and you know damn good and well that when they get a reliable product they're gonna release it as a kit.

(drum roll please)

Open Source Aviation!

No, I'm serious... when you buy a kitplane, you get the source (plans, etc.), and you are perfectly free to hack'em, and post your results and sell the resulting product. (Kindof a BSDish license... 1/2:) The original 2-seat pusher LongEZ became the 4-seat Velocity, the taildragger Quickie, and inspired the commercial LearStar and Beechcraft StarShip designs.

Yeah, aircraft design is kinda like doing something the size of Mozilla.. but once you've got something working (and the VariEze/LongEZ designs have been around for... well, the old VariViggen (the granddaddy of all homebuilt canards) the Museum of Flight was registered in 1972, so.... and once you've got something it's dead easy to do incremental improvement and even rapid prototyping.

They've been doing this on a shoestring budget (I know how the Rutan brothers work, that's how they built Voyager) for about two years now, and they've got a bird in the air alreddie... where the Zoche folks have been at this aerodiesel thing for six years now, and still don't have anything flying... which is a reflection of the design philosophy; Zoche is going for an FAR-23 certified engine up front, where XCOR is happy to get something off the ground in a safe manner... in much the same way as Netscape would write this huge thing ground-up and only release it when it was all done as opposed to Mozilla pumping out milestone after milestone as things gradually started working...

In short, real-world, non-code-geek example of why bazaar-style development works.

I hate to break this to the programming community, but you did not invent the philosophy of "open source" or the "bazaar vs. the cathedral."

Science has had an "open source" component for pretty much as long as there has been modern science. Everybody works on some little bit of the problem (figuring out how the universe works), and when they have something they think is reasonable they publish it for everyone else to critique. Such publications may not technically be free, because you have to subscribe to the journals, but in reality if you go to any science library you can get free access to them. Really, the philosophy of finding mistakes by releasing code as "open source" so that a lot of other people can look at it and tinker with it is the same old philosophy behind peer-review and publication of scientific papers. The "open source aircraft design movement" exists; it is called "Journal of Aircraft" and is delivered to my home every couple of months.

This may get me modded down, but I think that "open source" is just Computer Scientists figuring out something that the other branches of science have already known for a very long time. Getting new developments into the public domain and letting other researchers bang around on them will yield even newer and better developments. One team of people locked away in isolation is not nearly as likely to develop a workable product (which for science would pretty much be a model of everything in the universe.)

That said, I don't think the idea of developing aircraft the same way that you develop programs is a good idea, because they are NOT the same sort of things. I'm sure you all know the joke about if Airplane development went like Computer development then we'd already have hypersonic transport aircraft with world spanning range that the average person could afford to own and operate... and they would explode once every week or two killing everyone on board. Aircraft Theory and Aircraft Conceptual Design and Aerodynamic Behavior and other such things are generally done as public science and/or published in journals and presented at conferences (i.e. "open source"). When it gets time to actually design the aircraft, this is done with a relatively small, closed team of people. There is a good reason for this. Airplane and rocket crashes kill people. Pick up a copy of The Right Stuff and read the first chapter. Such things ARE tested regularly. They are tested methodically and often. In wind tunnels and CFD code and on the ground and finally in the air. They are tested with methods and in progressions that were proven to work with VERY costly (in dollars and lives) prior experience. You could call it "extreme programming" for aircraft. Aircraft design is also complex. Simply moving the battery from the front to the back of a plane this size can invalidate all previous flight test data, so it is with good reason that the development is done by people who know the whole picture intimately (a difficult thing for a hobbyist to do). And, many aircraft design groups don't want their detail designs and their "tricks of the trade" to be open source because they are proprietary or classified. Yes, other sciences have "Closed Source" projects, too; but unlike in computer science, they tend to usually be offshoots and niche developments with the bulk of science being "open source" (to use CS lingo). Even big, private company laboratories in other scientific fields publish a lot of "open source" scientific material. Not only do they realize the value of having it reviewed and verified by other scientists "for free," but they also understand the importance of such publication in maintaining their organization's prestige in their industry and in recruiting the best new talent.

Aerospace has had "open source" for almost 100 years now. Physics has had it since the days of Newton and Galileo. Computer scientists, welcome to the club. Just don't think the rest of us haven't known about this for a long time... and stop tacking the phrase "open source" on everything. Try terms like "peer review" and "in the public domain" on for size; maybe you'll sound less socialist and the public will take it more seriously.

Very insightful comment. As you point out, modern science is based on the free exchange of ideas. This shouldn't come as a suprise to anyone with a technical education.

However, there is one major difference between the general scientific community and the Open Source movement: scientists share abstract ideas, whereas OSS shares a useful, consumable product. An openly published physics paper is really only useful to other physicists. An openly published computer program is useful to anyone with a computer -- you don't have to be able to understand the source code in order to execute the program.

I find it unbelievably strange that John Carmack (of Doom,Quake fame) is also building a rocket capable of transporting humans. He's made a ton of progress. His company: Armadillo Aerospace [armadilloaerospace.com]

I'm very suprised to see nobody else in this forum recognize the name "Rutan." The Rutan brothers, especially Dick, are huge figures in experimental aviation. The Design that was modified for this experiment was originally created by Dick. As were many other novel and very successful airplanes. Among them were the "Voyager" aircraft that circled the globe unrefueled. He also has an "nonsymetrical" twin engined, twin hulled aircraft that carries eight people, goes 300mpg and is fully aerobatic.
Trust me, this guy knows his stuff and is quite unlikely to win the Darwin arward. Not saying can't, but given this guys intelligence and experience, I don't believe he could ever be a candidate.

In 1986 Dick Rutan flew his "Voyager" around the world, non-stop, in 9 days [dickrutan.com]. In 1997 he flew his Long-EZ around the world, with many stops, in 80-or-so days [dickrutan.com]. Now with his EZ-Rocket [dickrutan.com] maybe could now fly round the world, with refuelling stops, in (what?) a day?

Meanwhile, previous Long-EZ customer's will love this the Rocket-EZ. John Denver could've killed himself [256.com] much quicker in one of these. And James Gleick could make another - high speed - attempt on his own life [wired.com] too.

While I have no doubt that the rocketplanes test was a complete success, I do have some issues with its ultimate goal of low cost reusable orbital operations. Two 400lb rockets just arent going to cut it. Figure the plane wieghs in at 10 tons fully loaded, thats 20000 lbs of fuel, rocket and pilot, and wings. Wings are good for getting you up off the ground, which this demonstrated, but they really become a liability above say mach 3-4 and they are obviously completely useless once in space. Keep in mind that they only got up to about 160knots or maybe 200mph. Orbital velocity is 14000 mph. you need alot more oomph than 800 lbs of thrust to put you into a stable orbit.

XCOR is doing it just right. I've always felt that the way to space is paved with a market - a REAL market
not platimum mining fairy tales - a small group, and a small, non-gold
plated start. Equipment that's simple, tough, reliable, not cutting
edge.

I'll bet there is a market for Me-163 and X-1 replicas. Maybe not a
huge market but a market nevertheless.

There was a business in Texas building Me-262 replicas, full size,
exact in the airframe but using modern engines and avionics. They had
orders in hand, deposits, and airframes well under way. I stopped
following them some time ago and don't know if they delivered: last I
heard there were problems.

Get more people flying rockets - even if it's in the atmosphere at
subsonic speeds - and you've taken the first crucial step.

Get more people flying rockets - even if it's in the atmosphere at subsonic speeds - and you've taken the first crucial step.

The first crucial step to what ? More mindless resource burning ?

When I hear "vertical drag racing" I tend to choke. What exactly is good in that ?

If you want progress, go for old-fashioned horizontal drag-racing using electrical engines and suitable batteries. This might have an impact on technology advances in a sector that might essentially help save the planet by using different resources.

If you want more progress on old-fashioned combustion engines create a car-racing formula that essentially bases on getting the race done with a limited amount of fuel. This might boost engine efficiency.

Nobody is doing this right now. At least not to a commercially usable level. It just not where the money lurks.

Disclaimer: I am not a tree-hugger. I just think we don't need Formula1 teams with 800hp cars, that talk about "doing research for the cars on the road in 10 years". We don't need developing drag race technology that will never see any commercial use. And we certainly don't need vertical drag racing, as it is just old technology in the hands of the masses.

If you want progress, go for old-fashioned horizontal drag-racing using electrical engines and suitable batteries. This might have an impact on technology advances in a sector that might essentially help save the planet by using different resources.

.

Great! So how much extra coal or oil should we burn in power stations to generate the electricity to power these things?
Conventional forms of electic transport just move the pollution from one place to another..

Have you ever seen a solar-powered calculator? A wind-prop built up in offshore regions generating power for those living on the coast?

Just because America ignores the technology, it does not mean it is not there.

The entire point: gas(online) is still WAY too cheap in the United States. After all we know it might be gone in 30-50 years. So we'd better start getting into alternatives. Or we might end up fabriating very good walking shoes in the near future.

Of course you might say: These devices suck (solar and wind-energy), they have such a low efficiency. Well, take a look at convential combustion engines from 60 years ago. They sucked in terms of efficiency as well. Research made them better. Research can still make them better, but there are alternatives that deserve research just as much.

And i tend to think that a electrical engine has a higher power yield. Remember when you turn the ignition on your car (any car) next time: 75% of all the energy your gasoline/diesel can generate at all is WASTED (converted) into energies that don't serve forward motion: vibration, noise, engine heatup, friction...

The research done in racing does in fact make it to the road. Anti-lock brakes, traction control, and 'crush zones' all come from high-tech racing. Aerodynamics as well, which directly impact fuel effciency.

Agreed and point taken. What I am saying is: limit the gasonline usage even more. What will we see? Shorter races? Or again even better efficiency with a race getting even more kicks because a "technology race" is being held at the same time the drivers are battling for the lead position.

The up-and-down combustion engine is being used for lots of decades. What could be won with rotary engines? What can be archieved by restricting cars to 1liter-engines with twin-turbos. And what could be won (in terms of environment preservation) once these techniques make it to the showroom?

The rockets we are currently firing use hydrogen peroxide, which produces nothing but water and oxygen in the exhaust. Not even the most rabid greenie could argue with that.

Hydrogen / oxygen rockets also produce water and excess hydrogen. Alcohol / ocygen rockets leave a few other things similar to auto exhaust, but not really worse.

Solid rockets leave some bad stuff, and some propellants are truly nasty, like nitrogen tetroxide and hydrazine, but those are also much more expensive, so wouldn't be used in a cost effective program.

H2O2 is a walk in the park compared to liquid O2. Both are quite nasty, but people usually survive a dousing in 95% hydrogen peroxide: yes, you are porcelain white for a few weeks, but you live. That assumes you have a decent shower on-site (think water-tower, not hose-pipe.) O2 accidents of similar magnitude kill you: cryogenic freezing, plus O2 mixes with organics to form pressure-sensitive explosive slush.

LOX eats through bad rocket elements (e.g. below spec piping and valves) much faster than H2O2, and the low temp makes valve sticking and thermal mismatch failures much more likely.

To get equivalent safety, working with LOX will cost 10 times as much.

To get equivalent safety, working with LOX will cost 10 times as much.

Um, no, not really. First of all, high grade peroxide costs $0.50/lb for 70% grade in tankcar load quantities or larger, and $10/lb or so for 97% grade commercially concentrated (you can distill 90%+ yourself from 70%, but it requires significant processing equipment and has non-zero risk associated). LOX is cheaper than beer ($0.10/lb or less in large bulk quantities).

Second of all, handling liquid oxygen and nitrogen grade cryogenics is pretty easy. LOX is used in nearly all hospitals for their oxygen feeds; there's usually a LOX tank out in the parking lot somewhere. You have to avoid using organic materials in the piping, but it's handled by relatively low-trained truckers distributing it, in tanker truckload quantities, moved around cities with little hassle or hazmat risk, every day. It has risks, and must be properly respected, but is not a problem.

High-test peroxide is also subject to self-deomposition and detonation in extreme cases.

We have lively regular debates about the merits of various propellants in online forums like
sci.space.policy [news]
and
sci.space.tech [news].
Talk to professional rocket engineers and nobody is even vaguely afraid of LOX. It's not everybody's first choice, but it's not a bad one.

"Rocket Jets"? No, they did have a rocket powered plane, I have a book with the specs on it, but I don't have it with me at the moment. From what I recall, it was not a very useful aircraft as the rocket could only burn for about 10 minutes (not sure on the exact number).

I don't know about the 90% death rate, are you sure you're not confusing it with the Messerschmitt Bf 109? It was a traditional prop plane, but very high preformance and, thus, difficult to fly. The narrow wheel base and high landing speeds made it difficult to land, and the torque from the engine would sometimes cause pilots to lose control on takeoff. Also, the pilot could lose control in dives because the control surfaces were not big enough for the high speeds and the controls would become sluggish. The accident death rate was no where near 90%, but it was higher than other similar aircraft.

The Messerschmitt 262 was the famous German jet during the war. Here's [soton.ac.uk] a link to a page about it.

When people started looking to break the sound barrier, the British tried to do it with jets, but the Americans wisely decided that a supersonic jet would have too many complications, and decided to use a rocket powered aircraft to do it. The Bell X-1, flew by Chuck Yeager, was a rocket powered aircraft, but it landed as a glider, and appearently wasn't that difficult to land.

> XCOR wants to make replica planes of the ME163 AND the Bell X-1, using our modern (and SAFE) rocket
engines

Dude. This would rock.

Flying an ME163 must have been intense. Solving the engineering problems and creating replicas of these historic aircraft, even if it doesn't get anyone into space, gives every air show in North America one hell of a crowd-pleaser.

When I was a kid, I spent countless hours browsing through a big book of WWII planes. In the "funny looking" category, I certainly remember the Me-163, but I always found the Dornier Do-335 "Pfeil" [squadron13.com] even more fascinating.

"In early June 1927, rocket and space enthusiasts in Germany founded the Verein fuer Raumschiffahrt (Society for Space Travel). Some members experimented with black powder rockets.

Automobile manufacturer Fritz von Opel piloted his own rocket glider, Opel Rak.1, in tests near Frankfurt on 30 September 1928. Its 16 rockets, each producing 50 pounds of thrust, were build by Friedrich Sander a pyrotechnics specialist. The propulsion system combining high-thrust, fast-burning powder rockets for initial acceleration with lower-thrust, slower-burning rockets to sustain velocity.

Opel approached Alexander M. Lippisch, a young designer working at the Rhon-Rossitten-Gesellschaft, who had already displayed a penchant for the unorthodox in airplane configuration, with the proposal that he, too, design a glider for rocket power.

Max Valier and Alexander Sander also succeeded in arousing enthusiasm for rocket propulsion in a twenty- seven-year-old aircraft designer, Gottlop Espenlaub. His E 15 tail-less design was of interest as a rocketplane.

On 11 June, Fritz Stamer effected the first rocket- propelled flight in Lippish's glider. The glider had been dubbed Ente, or Duck. That lead later to the Lippish's Komet - the Messerschmitt Me 163, liquid rocket manned interceptor."

As I recall, Rutan is not trying to build rocketplanes. He wants to build VTO rockets.

The plane was just a way of testing the reliability of the rocket design on a real-world vehicle.

It isn't THE vehicle, guys, it's a testbed.

The final rocket will be something else entirely... and probably not built by Rutan. The company is looking to SELL the rocket engines, to companies who want to go to space. How they are used is not Burt's current concern.

Cheaper to use a Piper Cub to deliver a warhead. Don't obsess about rockets; the 1950's are a long time ago.

A rocket is expensive, shows up on intelligence radar, and has the bad habit of failing during flight. A small plane, a container vessel, a U-Haul, or a speedboat delivers the nuclear punch without the high-tech nonsense.

Remember, while Bush was touting invincible missle shields, we had the worst one-day disaster in civilian or military casualties, ever.